Method of manufacturing electrical contacts

ABSTRACT

A METHOD OF MANUFACTURING ELECTRICAL CONTACTS COMPRISES: FORMING A PLURALITY OF CONTACTS FROM A CONTINUOUS SHEET METAL BLANK SUCH AS THAT THE INDIVIDUAL CONTACTS ARE SPACED FROM EACH OTHER, BUT REMAIN CONNECTED TO OPPOSITE LONGITUDINAL EDGE STRIPS OF THE BLANK; REELING THE CONTACTS AND EDGE STRIPS INTO A COIL FORM; AND CLEANING, HARDENING, SURFACE TREATING, AND COATING THE CONTACTS WHILE IN THE COIL FORM, THE COATING BEING OF A METAL HAVING SUPERIOR ELECTRICAL CONDUCTIVITY AS COMPARED WITH THE BASE METAL OF THE ORIGINAL BLANK. ADDITIONALLY, THE METHOD MAY COMPRISE: UNREELING THE FIRST COIL; CUTTING THE EDGE STRIPS AT SELECTED LOCATIONS TO PROVIDE STRIPS OF CONTACTS OF A DESIRED LENGTH; REELING THE STRIPS INTO A PLURALITY OF SMALLER DIAMETER COILS AND SIMULTANEOUSLY INTERLEAVEING A DIVERSE METAL SEPARATOR BETWEEN THE LOOPS OF THE SMALLER COILS; AND TIN COATING THE TAILS OF THE CONTACTS TO RENDER SAME READILY SOLDERABLE TO WIRE LEADS.

.July 17, 1973 3,746,583

METHOD O1" MANUFACTURING lfiL-FKJ'IH'ICAL CONTACTS E. E. SIEGFRIEDT, JR. ET M Filed Oct. 27, 1971 FIG. I

United States Patent O 3,746,583 METHOD OF MANUFACTURING ELECTRICAL CONTACTS Ernest E. Siegfriedt, Jr., Winchester, and Otis H. Bramhall, Lexington, Mass., assignors to TRW Inc., Cleveland, Ohio Filed Oct. 27, 1971, Ser. No. 192,949 Int. Cl. C22f 1/00 US. Cl. 14813 2 Claims ABSTRACT OF THE DISCLOSURE A method of manufacturing electrical contacts comprises: forming a plurality of contacts from a continuous sheet metal blank such that the individual contacts are spaced from each other, but remain connected to opposite longitudinal edge strips of the blank; reeling the contacts and edge strips into a coil form; and cleaning, hardening, surface treating, and coating the contacts while in the coil form, the coating being of a metal having superior electrical conductivity as compared with the base metal of the original blank. Additionally, the method may comprise: unreeling the first coil; cutting the edge strips at selected locations to provide strips of contacts of a desired length; reeling the strips into a plurality of smaller diameter coils and simultaneously interleaving a diverse metal separator between the loops of the smaller coils; and tin coating the tails of the contacts to render same readily soldera'ble to wire leads.

BACKGROUND OF THE INVENTION The old method of tin dipping the tails of contacts was to take the individual contacts and move them in bulk in pans through the processes of degreasing, heat treating, descaling, plating and tin dipping. The tails of the contacts after heat treatment are desirably a little soft and are therefore vulnerable to being bent, stretched, twisted, or ortherwise distorted. The loose contacts in the pans tend to interlock and tangle due to the interengagement of the relief slots in the body of the contact and the tails. Tangling is frequently so severe that the contacts cannot be separated and have to be placed in salvage. Handling of the contact during the numerous transfers increases the danger of damaging the tails at all stages of the manufacturing process. Once the contacts are placed in their plastic housing. the possibility of damage is considerably reduced because the slots of the body of the contacts are masked by the housing.

SUMMARY OF THE INVENTION An object of the present invention is to reduce the danger of tangling and tail damage to contacts which are transferred in bulk.

Another object of the present invention is to provide a method of simultaneously tin dipping a number of contacts.

Still another object of the present invention is to provide a method of simultaneously applying manufacturing techniques to objects having fragile extensions.

By retaining the contacts in the frame formed by the stamping process, it is possible to perform manufacturing operations simultaneously on many contacts while reduc ing the danger of damaging the contacts.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top plan view of a coil of contacts;

FIG. 2 is an enlarged perspective view of a strip of contacts drawn from the coil shown in FIG. 1.

FIG. 3 is a diagrammatic view of a method of wave soldering the tails of the contacts while reeled in a smaller coil than that shown in FIG. 1;

3,746,583 Patented July 17, 1973 DESCRIPTION OF THE PREFERRED EMBODIMENT The press for manufacturing the contacts 10 produces a strip having the contact tails 12 attached to a top and bottom support strip 14 and 16. The contacts 10 are each spaced about of an inch apart and include a tubular body portion 18 having a series of spaced longitudinal relief slots 20 with a tail 12 extending from each end. The material from which the contacts 10 are made can be duo-metal, beryllium copper, brass, or Phosphor bronze. The strip 22 of contacts is coiled, treated to remove the production oils and other contaminants, and then is passed through an oven for heat treatment which consists of raising the temperature to 600 F. for three hours in a circulating air atmosphere. The coil is then descaled by passing it through a dilute sulfuric acid solution thereby removing any oxide coating from the copper without attacking the metal proper. The entire coil is then silver plated to improve contact conductivity, to prevent subsequent oxidation and to improve solderability. The coils are then uncoiled, stretched and cut into strips of predetermined lengths which are subsequently coiled into smaller coils that are interleaved with stainless steel separators 24, the separators having a generally sinuous profile in side elevation. The function of the separators is to maintain a uniform and minimum separation between loops of the coils. A coil(s) of contacts including the separator 24 is thereafter placed in a cage like basket 26 and carried by a belt 28 through a wave soldering ma chine 28, which includes a preheated fluxing station and a tin dipping station. After a first tin dipping the coil is turned over and the fiuxing and tinning is repeated on the other side thereby coating all the tails 12 of the contacts 10. The purpose of the tin dipping is to provide a highly solderable surface on the contact tails. Finally, the excess flux is removed by a chemical treatment.

The contacts 10 are subsequently cut from strips unreeled from the smaller coils and in many instances are installed in a plastic housing 30. This severing and installing is carried out automatically and it is therefore very important that the tails 12 of the contacts 10 be straight and parallel to each other in the installation to facilitate their ultimate mounting on a chassis such as a printed circuit board.

With reference to the foregoing description it is to be understood that what has been disclosed therein is illustrative of a preferred embodiment of the invention and is to be construed as illustrative rather than restrictive in nature. The invention is best defined by the following claims.

What is claimed is:

1. A method of manufacturing electric current carrying members comprising the steps of:

(1) forming a plurality of said members from a continuous blank of relatively malleable sheet metal such that the individual members are spaced from one another, but are connected to a common support means, said support means being opposite longitudinal edge strips of the original sheet metal blank;

(2) reeling said members and said edge strips into a coil form; and

(3) passing said coil through a series of treatments wherein said members are:

(a) cleaned to removed dirt and other contaminants therefrom; (b) hardened and rendered more resilient;

(0) surface treated to remove metallic oxide coatings therefrom; and

(d) coated with a metal having superior electric current carrying characteristics as compared with the base material of said blank.

2. A method according to claim 1 comprising the additional steps of:

(4) unreeling the first coil;

(5) severing said longitudinal edge strips at selected locations to provide continuous strips of said members of a desired length;

(6) reeling said strips of selected length into a plurality of coils which are smaller in diameter than said first coil and simultaneously interleaving a separator between the loops of said smaller coils; and

(7) coating at least a portion of each of said members, while in said smaller coils, with a metal which is different from both the base metal of the original blank and that which was applied as a coating in step 3(d) which metal is highly conducive to soldering, whereby said members are rendered readily solderable to electric current carrying conductors.

References Cited UNITED STATES PATENTS 2,891,304 6/1959 Colvin 29193.5 3,431,092 3/1969 Lehner 29-1935 3,469,953 9/1969 St. Clair et al. 29-1935 3,269,805 8/1966 Evans 29-190 RICHARD O. DEAN, Primary Examiner US. Cl. X.R. 

